EP0182436B1

EP0182436B1 - Process for the preparation of gasoline

Info

Publication number: EP0182436B1
Application number: EP85201862A
Authority: EP
Inventors: Huno Van Der Eijk; Jacobus Johannes Leonardus Heinerman; Ian Ernest Maxwell
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1984-11-22
Filing date: 1985-11-12
Publication date: 1990-08-22
Anticipated expiration: 2005-11-12
Also published as: DE3579294D1; US4620920A; EP0182436A2; AU5020685A; AR242625A1; CA1258245A; JPS61127789A; EP0182436A3; NL8403551A; AU576027B2; ZA858889B

Description

This invention relates to a process for the preparation of gasoline from hydrocarbon oils boiling above the gasoline range.
For the preparation of gasoline from hydrocarbon oils boiling above the gasoline range catalytic cracking is employed on a large scale. Gasoline preparation by catalytic cracking is carried out by contacting the hydrocarbon oil to be cracked at an elevated temperature with a cracking catalyst. Catalytic cracking on a technical scale is generally conducted in a continuous process by using an apparatus substantially consisting of a vertically arranged cracking reactor and a catalyst regenerator. Hot regenerated catalyst coming from the regenerator is suspended in the oil to be cracked and the mixture is passed through the cracking reactor in upward direction. Catalyst, which has become deactivated by carbon deposits is separted from the cracked product, stripped and then transferred to a regenerator, where carbon deposits are removed from the catalyst by burning them off. The cracked product is divided into a light fraction having a high C₃ and C₄ olefins content, a gasoline fraction, and several heavy fractions, such as a light cycle oil, a middle cycle oil, a heavy cycle oil and a slurry oil. In order to increase the yield of gasoline, one or more of the heavy product fractions can be recirculated to the cracking reactor, and the C₃ and C₄ olefins present in the light fraction can be converted by alkylation with isobutane into alkylate gasoline.
In catalytic cracking on a technical scale it is an objective to have the amount of heat which is released in the regenerator during the burning off of coke deposits from the catalyst correspond substantially with the amount of heat required in the cracking reactor, so that the process can be conducted without additional heating or cooling devices having to be installed. In determining reaction conditions under which the catalytic cracking process should be carried out, the reactor carbon requirement of the cracking unit and the Conradson carbon test value of the feed play an important role. The term "reactor carbon requirement" of the cracking unit (R as %w, calculated on catalyst) is used to designate the quantity of carbon that must be deposited on the catalyst in the cracking unit in order to achieve that the amount of heat released in the regenerator corresponds substantially with the amount of heat required in the cracking reactor. For a given feed the amount of carbon deposited in the cracking reactor on the catalyst will generally be larger according as the cracking is carried out under more severe conditions. According as a feed has a higher Conradson carbon test value (C as %w, calculated on feed), the cracking of that feed in a cracking unit under given conditions will generally lead to higher amounts of carbon being deposited on the catalyst in the cracking reactor.
A convenient criterion for assessing the suitability of feeds for a catalytic cracking unit in which cracking is carried out under such conditions that the quantity of carbon, which in the cracking reactor is deposited on the catalyst corresponds with R, is the quotient C/R. Generally, a feed will yield more gasoline according as the quotient C/R is lower.
During an investigation into the preparation of gasoline by catalytic cracking of hydrocarbon oils boiling above the gasoline range, at temperatures between 475 and 550°C, in a catalytic cracking unit having a value for R between 3 and 8%w, it has now surprisingly been found that the cracking of a mixture of two hydrocarbon oils can result in a gasoline yield which is much higher than expected under the assumption of linear mixing. In order to attain said increase in gasoline yield, one of the two mixing components should be chosen from the group formed by hydrocarbopn oils having a C/R > 0.8, whilst the other mixing component should be chosen from the group formed by hydrocarbon oils having a C/R < 0.2 and which component in addition has a basic nitrogen content (N) of less than 150 ppmw and a tetra⁺ aromatics content (T) of less than 3%w. It has been unexpectedly found that if the two mixing components are well chosen, 20% more gasoline can be prepared from such mixtures than expected to date under the assumption of linear mixing.
The present invention therefore relates to a process for the preparation of gasoline, wherein a mixture of hydrocarbon oils boiling above the gasoline range, is subjected to catalytic cracking at a temperature between 475 and 550°C and a pressure of 1-10 bar in a catalytic cracking unit having a reactor carbon requirement (R) between 3 and 8%w, which mixture comprises a first hydrocarbon oil having a Conradson carbon test value (C in %w) such that the quotient C/R is higher than 0,8, and a second hydrocarbon oil having such a value for C that the quotient C/R is lower than 0.2, and wherein said second hydrocarbon oil has a basic nitrogen content (N) of less than 150 ppmw and a tetra aromatics content (T) of less than 3%w. The tetra⁺ aromatics content (T) is defined as the fraction of hydrocarbon molecules having four or more aromatic rings.
In the process according to the invention the two mixing components should have a C value such that the difference between the quotients C/R of the mixing components is bigger than 0.6. Preferably, the mixing components have a C value such that said difference is bigger than 0.8. It is preferred that one of the two mixing components has a C value such that the quotient C/R is higher than 0.9, whereas the other mixing component preferably has a C value such that the quotient C/R is lower than 0.1. As for the values for N and T of the mixing component having a C value such that the quotient C/R is lower than 0.2, preference is given to hydrocarbon oils having an N value of less than 100 ppmw and to hydrocarbon oils having a T value of less than 2%w.
In the process according to the invention one preferred mixing component having a C value such that the quotient C/R is higher than 0.8 is a residue obtained in the distillation of a crude mineral oil, which residue has optionally been subjected to a deasphalting treatment. Both distillation residues obtained in the atmospheric distillation of a crude mineral oil and distillation residues obtained in the vacuum distillation of an atmospheric residue of a crude mineral oil are eligible as mixing components. Special preference is given to the use of atomospheric distillation residues. A preferred mixing component having a C value such that the quotient C/R is lower than 0.2 is a heavy distillate obtained in the distillation of a crude mineral oil, which distillate has optionally been subjected to a catalytic hydrotreatment. Both heavy distillates obtained in the atmospheric distillation of a crude mineral oil and distillates obtained in the vacuum distillation of an atmospheric residue of a crude mineral oil are eligible as mixing components. Special preference is given to hydrocarbon oils which have been prepared by applying a catalytic hydrotreatment to a distillate obtained in the vacuum distillation of an atmospheric distillatioon residue of a crude mineral oil. A vacuum distillate subjected to catalytic hydrotreatment preferably has a C value such that the quotient C/R is lower than 0.4 and a value for N of more than 300 ppmw and a value for T of more than 2.9%w. The catalytic hydrotreatment of the vacuum distillate is preferably carried out at a temperature of 275-450°C and in particular of 300-425°C, a hydrogen pressure of 25―80 bar and in particular of 30-70 bar, a space velocity of 0.1-5 1.1^-1.h^-1 and in particular of 0.2-3 1.1^-1.h^-1 and H₂/feed ratio of 100-2000 Nl.kg^-1 and in particular of 200-1500 Nl.kg^-1. A preferred catalyst for the hydrotreatment is a sulphided catalyst comprising nickel and/or cobalt together with molybdenum and/or tungsten supported on alumina, silica or silica-alumina as the carrier.
The weight ratio of the two components in the specified mixture which is catalytically cracked according to the invention may vary within wide ranges. Preferably mixtures are used for which the weight ratio of the two components lies between 30:70 and 70:30 and in particular between 40:60 and 60:40.
The catalytic cracking according to the invention is preferably carried out at a temperature of 485-540°C and in particular of 495-530'C, a pressure of 1-10 bar and in particular of 1.5-7.5 bar, a space velocity of 0.25-4 kg.kg^-1.h^-1 and in particular of 0.5-2.5 kg.kg^-1.h^-1 and a catalyst renewal rate of 0.1-5 and in particular of 0.2-2, kg of catalyst per 1000 kg of feed. In the catalytic cracking preference is given to the use of a zeolitic catalyst.
The invention is now illustrated with the aid of the following example.

Example

In order to prepare gasoline with boiling range C_S-221°C, there were carried out in a catalytic cracking unit having a value for R of 5%w, nine experiments (Experiments 1-9) in which a Feed 1, a Feed 2 and various mixtures of Feed 1 and Feed 2 were contacted at a temperature of 510°C, a pressure of 2 bar and at various space velocities with a zeolitic cracking catalyst.
Feed 1 was a 370°C⁺ residue obtained in the atmospheric distillation of a crude mineral oil. Feed 1 had the following properties:

T = 5.32%w; N = 731 ppmw; C = 5.1%w and, therefore, C/R = 1.02.

Feed 2 was prepared starting from a 370-520°C distillate obtained in the vacuum distillation of an atmospheric distillation residue from a crude mineral oil. The vacuum distillate from which Feed 2 was prepared had the following properties:

T = 4.65%w; N = 461 ppmw; C = 1.1 %w.

In order to prepare Feed 2, this vacuum distillate was subjected to a catalytic hydrotreatment by contacting it at a temperature of 380°C, a hydrogen pressure of 54 bar, a space velocity of 0.9 g.g.^-1.h^-1 and a H₂/feed ratio of 400 Nl.kg^-1 with a Ni/Mo/AI₂0₃ catalyst. Feed 2 was obtained as the 370°C⁺ residue in the atmospheric distillation of the hydrotreated product. Feed 2 had the following properties:

T = 2.5%w; N = 30 ppmw; C = 0.4%w and, therefore, C/R = 0.08.

The results of the catalytic cracking experiments as well as the space velocities used in each of the experiments are given in the Table. For each experiment are given in the Table the experimentally found yield of C₅―221°C gasoline, the expected yield of gasoline, calculated under assumption of linear mixing according to the formula:
and the gain in gasoline yield expressed as

Claims

1. A process for the preparation of gasoline, which comprises subjecting a mixture of hydrocarbon oils boiling above the gasoline range to catalytic cracking at a temperature between 475 and 550°C and a pressure of 1-10 bar in a catalytic cracking unit having a reactor carbon requirement (R) between 3 and 8%w, which mixture comprises a first hydrocarbon oil having a Conradson carbon test value (C in %w) such that the quotient C/R is higher than 0.8 and a second hydrocarbon oil having a C value such that the quotient C/R is lower than 0.2 and wherein said second hydrocarbon oil has a basic nitrogen content (N) of less than 150 ppmw and a tetra⁺ aromatics content (T) of less than 3%w.

2. A process as claimed in claim 1 wherein hydrocarbon oils are used having such values for C that the difference between the quotient C/R is bigger than 0.8.

3. A process as claimed in claim 1 or 2 wherein a first hydrocarbon oil is used having a C value such that the quotient C/R is higher than 0.9 and a second hydrocarbon oil having a C value such that the quotient C/R is lower than 0.1.

4. A process as claimed in any one of claims 1-3 wherein a hydrocarbon oil is used having a C value such that the quotient C/R is lower than 0.2, a value for N of less than 100 ppmw and a value for T of less than 2%w.

5. A process as claimed in any one of claims 1-4 wherein use is made of a residue obtained in the distillation of a crude mineral oil, which residue has optionally been subjected to a deasphalting treatment as hydrocarbon oil having a C value such that the quotient C/R is higher than 0.8.

6. A process as claimed in claim 5 wherein use is made of an atmospheric distillation residue obtained from a crude mineral oil as hydrocarbon oil having a C value such that the quotient C/R is higher than 0.8.

7. A process as claimed in any one of claims 1-6 wherein use is made of a heavy distillate obtained in the distillation of a crude mineral oil, which distillate has optionally been subjected to a catalytic hydrotreatment as hydrocarbon oil having a C value such that the quotient C/R is lower than 0.2.

8. A process as claimed in claim 7 wherein use is made of a hydrocarbon oil which has been prepared by applying a catalytic hydrotreatment to a distillate obtained in the vacuum distillation of an atmospheric distillation residue from a crude mineral oil as hydrocarbon oil having a C value such that the quotient C/R is lower than 0.2.

9. A process as claimed in claim 8 wherein the vacuum distillate subjected to the catalytic hydrotreatment has a C value such that the quotient C/R is lower than 0.4, a value for N of more than 300 ppmw and a value for T of more than 2.9%w.

10. A process as claimed in any one of claims 7-9 wherein the catalytic hydrotreatment is carried out at a temperature of 275―450°C, a hydrogen pressure of 25-80 bar, a space velocity of 0.1-5 1.1^-1.h^-1 and a H₂/feed ratio of 100-2000 Nl.kg^-1.

11. A process as claimed in any one of claims 7-10 wherein in the catalytic hydrotreatment a sulphided catalyst is used comprising nickel and/or cobalt together with molybdenum and/or tungsten supported on alumina, silica or silica-alumina as carrier.

12. A process as claimed in any one of claims 1-11 wherein use is made of a mixture to be cracked having a weight ratio of the two components between 30:70 and 70:30.

13. A process as claimed in claim 12 wherein use is made of a mixture to be cracked having a weight ratio of the two components between 40:60 and 60:40.

14. A process as claimed in any one of claims 1-13 wherein the catalytic cracking is carried out at a temperature of 485-540°C, a pressure of 1-10 bar, a space velocity of 0.25―4 kg.kg^-1.h^-1 and a catalyst renewal rate of 0.1-5 kg of catalyst per 1000 kg of feed.

15. A process as claimed in any one of claims 1-14 wherein use is made of a zeolitic catalyst in the catalytic cracking.